The present invention relates to a magnetic disk driving device for recording information on, or retrieving recorded information from a disk-shaped magnetic recording medium.
A magnetic disk driving device for recording/retrieving information on/from a disk-shaped magnetic recording medium (which will be hereinafter referred to as a disk) is widely used as an external storage for an information processing device such as a computer and a word processor. The disk is generally classified into a hard disk formed from a hard base and a flexible disk formed from a flexible base. In a hard disk device using the hard disk, a floating head slider is used to float a magnetic head from a recording surface of the hard disk at a very small distance during the recording/retrieving operation. On the other hand, in a flexible disk device using the flexible disk, a magnetic head is maintained in sliding contact with the disk during the recording/retrieving operation. In the hard disk device, the hard disk is rotated at high speed. Therefore, if a solid contacts the recording surface of the disk during rotation of the disk, the recording surface will be damaged to cause destruction of information recorded. For this reason, the floating head slider is used in the hard disk device. Thus, while the hard disk has a large memory capacity, it is cumbersome to handle.
In the flexible disk device, a rotating speed of the flexible disk is lower than that of the hard disk, and a memory capacity is also smaller than the hard disk because of a larger track width. However, since the base of the flexible disk is flexible, an external force applied to the disk upon contacting or sliding of the magnetic head thereon is released by deformation of the base, thereby preventing the recording layer on the base from being damaged. That is, as compared with the hard disk, the flexible disk is easy to handle although the memory capacity is small.
Meanwhile, the information processing device has recently been made compact. For example, the use of a hand-held (laptop) computer and a personal word processor have spread. Accordingly, an external storage to be mounted in these equipments is greatly desired to be made also compact. At present, a so-called 3.5-inch diameter hard disk device or flexible (floppy) disk device is mounted in these equipments. However, it is desired to develop a flexible disk device having a large memory capacity because the hard disk device is weak against vibration or impact, and it has no compatibility of the disk.
An example of the conventional flexible disk device is disclosed in U.S. Pat. No. 3,879,757.
In the conventional flexible device, a plurality of disks cannot be mounted for recording/retrieving of information as in the hard disk device, and it is therefore hard to remarkably increase a memory capacity. Furthermore, the conventional flexible disk device is required to move a carriage for supporting a magnetic head with a high positioning accuracy, so as to provide the compatibility of the disk. Accordingly, the smaller are made a track width and a track pitch (frequency) of the disk to meet the requirement of high-density information recording, the harder is obtained the compatibility of the disk.